(1) Field of the Invention
The invention relates to imaging arrays, and, more particularly, to a method for an imager having dual row access capability.
(2) Description of the Prior Art
Standard CMOS Active Pixel Sensors (APS) utilize a row scanning architecture for addressing pixel data and for generating an image frame. By sequentially scanning each row of the imager, a full image is generated in what is known as a progressive scan format. Color images use standard mosaic filter patterns that are placed directly over the imaging pixels to break up the image into its basic color components. Primary color filters break up the image into the red, green, and blue components while complimentary filters break up the image into yellow, cyan, and magenta components.
Standard patterns are commonly used to enable standardized production methods to be used. The most common standardized pattern is the Bayer pattern 25 shown in FIG. 2. As shown in FIG. 2, the Bayer pattern is an array comprising 2×2 pixel sub-arrays. Each 2×2 sub-array 25 comprises, from left to right, a red pixel followed by a green pixel in the first row 100 and, from left to right, a green pixel followed by a blue pixel, in the second row 101. This arrangement, in turn, results in, from top to bottom, a red pixel followed by a green pixel in the first column 200, and, from top to bottom, a green pixel followed by a blue pixel in the second column 201. This 2×2 sub-array 25 is repeated many times to create a large imager pixel array such as is shown in FIG. 3.
To correctly recreate the color image instant upon the imager array at a first pixel, it is necessary to combine, in proper proportions, the signal at the first pixel with a second and a third pixel. Specifically, the color signals from second and third pixels adjacent to an arbitrary chosen first pixel supply the additional color signals necessary to correctly demultiplex the first pixel color signal. If, for example, the first pixel is a green filtered pixel, then the color signals from the adjacent blue and red filtered pixels would be proportionally combined with the green pixel signal to correctly recreate the color for the green pixel location. It can be readily seen from the array configurations of FIGS. 2 and 3 that the color pixel signals from two lines or rows of the array are needed to fully recreate or demultiplex any given pixel.
Most CMOS imagers utilize either a random y or a random x and y addressing architecture. These architectures allow the imagers to be read using either progressive or interlaced scanning methods. These imagers allow a single line of pixels to be read on any single access. A row or line is selected and then read. Successive line reads are then performed to build a frame. In order to achieve full color reproduction from an imager, the current imager line data must be combined with a previously read line as discussed above. Therefore, a memory must be used to store the results of previous imager line reads so that they can be combined with current data.
Several prior art inventions relate to methods to read or to manipulate image data. U.S. Pat. No. 5,742,325 to Curry et al describes a printer apparatus for rendering image data on a recording medium. Two channels are used to read data such that data can be further processed according to one of two methods: half-toning for picture data and thresholding for line art or text. U.S. Pat. No. 6,243,100 B1 to Curry et al teaches an imager processing system for interpolation performance.